Such a tap is known from NL2003205. The known tap is provided with a tap outflow having a first channel and a second channel, the tap outflow being provided with:                a first conduit which bounds the first channel;        a second conduit which bounds the second channel; and        a jet aerator provided with a jet aerator housing which forms a downstream end of the tap outflow.        
With the known tap, both boiling and mixed water can be tapped, via two separate channels within one tap outflow. The known tap outflow is provided with two concentric channels: a central channel that is bounded by an inner wall and which in the known tap serves for passing through boiling water. The outflow is further provided with an outer wall which, together with the inner wall, bounds a ring channel which serves for passing through mixed water. In the known tap the outer wall also forms the outer casing of the tap outflow. The jet aerator makes the jet of water from the central channel or the ring channel ‘softer’ and more regular. This is desired for drawing off both kinds of water. It is preferred to use one jet aerator for both streams, not only because such a configuration is simpler to realize but also because it is visually desirable for the tapped water to flow out of the outflow mouth with a full jet.
DE102008006255A1 shows a similar tap, where, however, the channels are not concentric. In a variant, it is proposed in that publication to keep the two water channels separate by passing one channel through the jet aerator. Water coming from that channel is therefore not aerated and made “soft” by a jet aerator. A similar construction whereby one channel is aerated and the other channel is not, is known from an exemplary embodiment described in GB 2 104 625.
A jet aerator is known per se and breaks up the massive liquid jet in a tap outflow into a large number of very thin jets in that the pipe pressure presses the water through a ‘jet breaker’ which forms the top of the jet aerator housing. The jet breaker is provided with a jet breaker wall comprising one or more layers of material which are provided with liquid passage openings, for example in the form of meshes or orifices. This jet breaker wall not only breaks up the water mass into small jets but also provides for acceleration of the water in that the effective cross section of liquid passage openings is significantly smaller than the pipe cross section. In the known jet aerators, below the jet breaker is an aeration chamber. The aeration chamber is in communication with the environment via the air supplies having an entrance that opens into the environment and an exit that opens into the aeration chamber. The air supplies may be designed, for example, as slots provided circumferentially in the jet aerator housing. The accelerated thin water jets which have been formed by the jet breaker create in the aeration chamber a reduced pressure (venturi effect) as a result of which ambient air is drawn in via the air supplies. Thereupon this air is entrained and mixed with the thin water jets in the aeration chamber.
The bottom part of the jet aerator is formed by a series of wire meshes or similar mats. The aerated jets are here aligned and proceed to egress in a more regular and calmer pattern.